The present invention relates to a flexible light-weight polymer actuator that is deformed upon receipt of an electrical stimulus, and applicable to home-service robots and the like.
With respect to a driving source for a joint driving mechanism used for conventional industrial robots, devices such as an electromagnetic motor, a hydraulic actuator, and a pneumatic actuator are used. The joint driving mechanisms using such driving sources include a mechanism using an electromagnetic motor and a reduction mechanism mainly made of metal as well as a mechanism using a hydropneumatic cylinder made of metal, and are made of a hard heavy material, and used under control at a specific place in a factory.
In contrast, with respect to the driving source used for apparatuses such as robots that are expected to be actively operated closely to people for jobs, such as house chores and work assist jobs as well as nursing assist jobs for the aged and physically-challenged person, in homes, offices, and hospitals, there have been demands for allowing the driving source itself to be small-sized, light-weight and flexible, and also to be used safely. With respect to such an actuator, among the pneumatic actuators, a pneumatic actuator made from rubber, which is highly flexible, has been proposed; however, in order to drive this, auxiliary machineries such as a compressor and a controlling valve are required, with the result that the weight-reducing attempt for the entire system has a limitation. Here, artificial muscle actuators using various polymer materials that are light-weight and highly flexible have been proposed, and the practical use thereof has been desired.
With respect to the polymer actuators that are operated by an electric stimulus, Non-Patent Document 1 has described those as a key-note lecture. With respect to a polymer gel, a metal composite ion polymer, an inherently conducting polymer, a polymer having a carbon-based material dispersion-type conductivity, carbon-nano-tubes, and dielectric elastomers, polymer actuators that are driven by an electric stimulus have been examined. Among these, the inherently conducting polymer has been highly expected as an actuator which can be driven with a comparatively low voltage, provides a generated stress that exerts a capability exceeding a biological muscle, and has light-weight and flexible features.
Moreover, a polymer material having conductivity with a carbon-based material dispersed therein, for example, a polymer material having conductivity with carbon-nano-tubes dispersed therein have also been highly expected as actuators that exert a high generated force.
Conventionally, most of these polymer actuators are operated in an electrolytic solution. With respect to an example of an actuator that can be operated in the air, Patent Document 1 has disclosed a bent type actuator in which a solid-state electrolyte is sandwiched between two films made of an inherently conducting polymer, which are compatibly used as electrodes and active member layers. Moreover, with respect to another example of the same type of actuator that can be operated in the air, Patent Document 2 has disclosed an actuator of a translation type in which an electrolytic layer is sandwiched between a conductive polymer layer to form an active member layer and an opposing electrode.
Patent Document 1: Japanese Unexamined Patent Publication No. 11-169394
Patent Document 2: Japanese Unexamined Patent Publication No. 2005-51949
Non-Patent Document 1: S G. Wax, R. R. Sands, Smart Structures And Materials 1999: Electroactive Polymer Actuators and Devices, Proc. SPIE, Vol. 3669, pp. 2-10, 1999
In the structure of the bent type actuator shown in Patent Document 1, however, the movement of the actuator is limited by deflection, with the result that, although a comparatively large displacement can be obtained, the actuator fails to exert a great force due to low deflection rigidity.
Moreover, Patent Document 2 has disclosed, for example, the actuator in which, with respect to an actuator operable in the air, a conductive polymer is expanded and contracted to be deformed in the longitudinal direction, which is different from the deflection deformation, and string-shaped inherently conducting polymer materials, which are compatibly used as an electrode and an active member layer, are placed in the center of a column-shaped solid-state electrolyte, with electrodes facing the periphery of the column-shaped solid-state electrolyte being formed; however, the conductive polymer portion that is expanded and contracted as the actuator has a cylinder shape, and the resulting issue is that, when bundled, the effective cross-sectional area of the active member layer, which contributes to driving, becomes smaller.
In contrast, Patent Document 2 has disclosed the translation type actuator having laminated layers, which is capable of increasing the effective cross-sectional area of the active member layer, and also exerts a great force. In the actuator of this type, however, in the case when the electrolytic layer is made softer so as not to disturb the expansion and contraction of the active member layer, after repetitive operations with a large distortion generated in the active member layer, an interlayer separation tends to occur.
Here, with respect to the driving source used for apparatuses such as robots that are expected to be actively operated closely to people for jobs, such as house chores and work assist jobs as well as nursing assist jobs for the aged and physically-challenged person in homes, offices, and hospitals, there have been strong demands for achieving a small-size, light weight, and flexible driving source for an actuator and for consequently realizing a safe actuator.
In order to solve the above-mentioned issues, the present invention relates to a safe actuator using such a small-size, light weight, and flexible driving source, and its objective is to provide a polymer actuator using a polymer material, which can generate a great force, and is operated at high speeds, easily manufactured and in particular, highly resistant to deformation.